Calibration/Tolerance

DJJohnson70

How can I calibrate the time base? We have a very consistent mechanical signal and are experiencing approximately 5% error in time (0.47%) on the first scope (of 106 units) being deployed. The real time between pulses is 83.1ms, confirmed using Tektronix 3054 scope and again with stopwatch over several thousand pulses (3 mechanical revolutions, 1227 pulses per revolution, 102 seconds per revolution). Using the scope over 10 pulses we should see 831ms, but we are actually seeing 870ms. I would like to send out each unit calibrated to a known signal.

Hanno

Please upload a screenshot of your signal- it may be possible to change timescale/vertical resolution to improve the signal to get a more accurate reading. You can also try the latest:
http://forums.parallax.com/showthread.php/123627-Latest-PropScope-software
Hanno

DJJohnson70

Here is a screenshot at 100ms per div. The machine runs at constant speed, and 10 pulses should be 831ms. The fleet (100 machines) verifies the 831ms monthly using the current Tektronix scopes, but we are deploying the Propscope to be more portable and user friendly. Once I went through the test process, I found that instead of 831ms I am getting ~870ms. A significant error. I confirmed again with the Tektronix. The second is a photo from my phone of the Tektronix screen. Sorry for that, but I don't carry 3.5" floppies anymore.

Publison

Any updates on this problem?

It looks like a significant deviation.

Hanno

Happy New Year!
This bug introduced a 5% timing error when in streaming mode (using a timescale slower than 50ms/div). I've fixed it in v2.07. (http://forums.parallax.com/showthread.php/123627-Latest-PropScope-software)
I've recreate your signal by having the PropScope generate a 12 Hz signal and then measuring it at 100 mSec/div, see below for result:

Hanno

DJJohnson70

That update was fantastic! I now get the 831ms expected. Thank you, Hanno! Dan

Publison

Thanks for the nice update Hanno!

May you have a rumble free Happy New Year.

Jim

Hanno

Thanks Jim!
Haven't felt any shakes for close to a year (knocks wood). Did have a bad bike accident "central cord syndrome", slowly recovering...
Hanno